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  3. 共用题干 Clone FarmFactory farming could so

共用题干 Clone FarmFactory farming could so

天天题库2019-12-17  44
问题 共用题干Clone Farm
Factory farming could soon enter a new era of mass production .Companies in the US are developing the technology needed to"clone"chickens on a massive scale.Once a chicken with desirable traits has been bred or genetically engineered,tens of thousands of eggs,which will hatch into identical copies,could roll off the production lines every hour. Billions of clones could be produced each year to supply chicken farms with birds that all grow at the same rate,have the same amount of meat and taste the same.
This,at least,is the vision of the US's National Institute of Science and Technology,which has given Origen Therapeutics of Burlingame,California,and Embrex of North Carolina $4 .7 million to help fund research.The prospect has alarmed animal welfare groups,who fear it could increase the suffering of farm birds.
That's unlikely to put off the poultry industry,however,which wants disease-resistant birds that grow faster on less food."Producers would like the same meat quantity but to use reduced inputs to get there,"says Mike Fitzgerald of Origen.To meet this demand,Origen aims to"create an animal that is effectively a clone",he says.Normal cloning doesn't work in birds because eggs can't be removed and implanted.Instead,the company is trying to bulk-grow embryonic stem cells taken from fertilized eggs as soon as they're laid."The trick is to culture the cells without them starting to distinguish,so they remain pluripotent,"says Fitzgerald.
Using a long-established technique,these donor cells will then be injected into the embryo of a freshly laid,fertilized recipient egg,forming a chick that is a"chimera".Strictly speaking a chimera isn't a clone,because it contains cells from both donor and recipient. But Fitzgerald says it will be enough if,say,95 percent of a chicken's body develops from donor cells."In the poultry world,it doesn't matter if it's not 100 percent."he says.
Another challenge for Origen is to scale up production .To do this,it has teamed up with Embrex,which produces machines that can inject vaccines into up to 50,000 eggs an hour. Embrex is now trying to modify the machines to locate the embryo and inject the cells into precisely the right spot without killing it.
In future,Origen imagines freezing stem cells from different strains of chicken.If orders come in for a particular strain,millions of eggs could be produced in months or even weeks.At present, maintaining all the varieties the market might call for is too expensive for breeders and it takes years to bread enough chickens to produce the billions of eggs that farmers need.
选项 According to the first paragraph,which statement is the best description of the new era of factory farming?A: Eggs are all genetically engineered.B: Thousands of eggs are produced every hour.C: Cloned chickens are bulk-produced with the same growth rate,weight and taste.D: Identical eggs can be hatched on the production lines.
答案C
解析第一段最后一句提供了直接的答案。 第二段共提到三个研究机构和一个民间组织。the US's National Institute of Science and Technology为研究提供了经费，被资助的研究机构是Origen Therapeutics of Burlingame, California和Embrex of North Carolina。因此，A是答案。 原句的意思有两点是关键的，即每只鸡提供的肉量不变，但饲料（inputs）要减少。只有D符合原意。 该段第二句中which引导的从句表明，是Embrex生产疫苗注射装置，而不是两家研究单位共同研制。Embrex在此基础上将装置改造为细胞注射装置。所以，只有C最接近原意。 第六段的大意是，如果能冷冻所有品种的鸡的干细胞，那么，无论需要什么品种的鸡蛋或多少数量，都不是问题。但是，目前储备所有品种是非常昂贵的。B、C、D从几个方面表达了这层意思。因此，只有A是答案。
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